If you are thinking of looking up the topic mariachi opera in your handy music dictionary—don’t bother. It won’t be there. Mariachi opera is a new musical genre that emerged full-blown in Houston, Texas, in the first decade of the 21st century. In 2007, Anthony Freud, General Director of Houston Grand Opera, attended a performance of Mariachi Vargas de Tecalitán and was captivated by music of this accomplished ensemble. He was also a bit jealous of the audience’s exuberant vocal response to the performance, a far cry from the sedate applause of his opera audiences. He wondered if the two…